Mary Tyler Moore says she is "absolutely devastated" by former co-star and longtime friend Valerie Harper's cancer diagnosis."Valerie has given so much joy, laughter and love to the world," Moore said in a statement to People. "I join her fans ...

"Valerie has given so much joy, laughter and love to the world," Moore said in a statement to People. "I join her fans and send much love and positive thoughts to her and her family during this difficult time."

On Wednesday, Harper revealed that she had been diagnosed with terminal brain cancer in January and that she has just months to live. Harper, 73, and Moore, 76, shared the small screen on The Mary Tyler Moore Show from 1970 to 1974 before Harper's character, Rhoda, received her own spin-off. In 2011, Moore herself underwent surgery for a benign tumor in the same area of the brain where Harper's malignant cancer cells are located.

In her interview with People, Harper revealed that she called Moore the day before she went public with her diagnosis. After some small talk, "She said, 'What's up?'" Harper told the magazine. "I said, 'It's incurable cancer.' She said, 'Val, I'm so sorry.'" In addition, Harper said Moore gave her some important advice. "Mary said, 'One day at a time,'" Harper said. "That's how we've got to live our lives. That's the best we can do."